Research papersObserved variability in soil moisture in engineered urban green infrastructure systems and linkages to ecosystem services
Introduction
Soil-water-climate and vegetation interactions jointly determine the ability of landscapes to provide a range of ecosystem functions and services (Costanza et al., 1997, MEA, 2005). Soil moisture, in particular, is directly related to photosynthesis (Galmés et al., 2007a, Pinheiro and Chaves, 2010), plant respiration (Burton et al., 1998, Galmés et al., 2007b), nutrient metabolism, gross and net primary productivity (Churkina and Running, 1998, Nemani et al., 2003, Ciais et al., 2005, Guo et al., 2016), biomass allocation (Comeau and Kimmins, 1989, Xu et al., 2010), surface vegetation cover and health (Adegoke and Carleton, 2002), carbon (Pastor and Post, 1986, Williams and Albertson, 2004, Kurc and Small, 2007) and nitrogen fluxes (Pastor and Post, 1986), as well as to the productivity-response patterns to rainfall pulses (Odum et al., 1995, Guo et al., 2016), and is thus a key determinant of landscape ecohydrology (Rodriguez-Iturbe, 2000). Though spatio-temporal patterns in soil moisture are, and have, been of keen interest to a wide range of researchers for some time (Famiglietti et al., 2008, Korres et al., 2010, Korres et al., 2013, Korres et al., 2015, Koyama et al., 2010, Rosenbaum et al., 2012, Vereecken et al., 2014, Dorigo et al., 2015, Huang et al., 2016), there is new interest in the topic today as city managers introduce nature-based solutions like engineered green infrastructure (GI) into the urban landscape (WWAP (United Nations World Water Assessment Programme) (2018)).
In the last 1.5 decades, since GI was first proposed as an approach to urban stormwater management (Kloss et al., 2006), many researchers (Revelli and Porporato, 2018, Escobedo et al., 2019, Miller and Montalto, 2019) have espoused the wide range of ecosystem services (ES) that GI can provide. There is great interest in the ability of urban forests, distributed vegetated stormwater retention facilities (e.g. bioretention), and newly enhanced, restored, or created aquatic, riparian, and terrestrial habitats to intercept precipitation in the canopy, evapotranspire moisture from the soil, and otherwise regulate temperature (Susca et al., 2011), mitigate pollution of the air and water (Pugh et al., 2012, Jayasooriya et al., 2017), sequester carbon, and enhance human well-being (Bertram and Rehdanz, 2015, Rai et al., 2019). As GI implementation has proceeded, it has also become clear that GI can also provide a range of ecosystem disservices (EDS) (Lyytimäki and Sipilä, 2009). For example, GI systems can attract vectors, pests, or pollen-producing vegetation.
Table 1, modified and adapted from Miller and Montalto (2019) is an attempt to summarize the role that soil moisture plays in determining the ability of GI to provide ecosystem functions and services/disservices, disaggregated by domain (e.g. air, soil, water, and human), and focusing on bioretention. Many of these services/disservices are dependent on vegetation, the health of which is determined by moisture availability. Soil moisture constrains the rate of evapotranspiration, modifying both water and energy balances (Petropoulos, 2013). The actual rate of ET modulates the partitioning of incoming radiation into latent and sensible heat, and the partitioning of incident precipitation into infiltration and runoff (Western et al., 1999).
This paper is part of a broader effort to study interactions between soil, water, climate, and vegetation in GI systems (DiGiovanni et al., 2012, DiGiovanni et al., 2018, Alizadehtazi et al., 2016, Alizadehtazi et al., 2020, De Sousa et al., 2016a, De Sousa et al., 2016b, Smalls-Mantey, 2017, Alizadehtazi, 2018). Here, we analyze several years of soil moisture data collected in two bioretention facilities that are similar in design and monitoring set up and that are located within two kilometers of one another. Specifically, we quantify the role of precipitation characteristics, season, and hydraulic loading ratio (the ratio of the tributary catchment area to the facility area, HLR) on soil moisture at different depths, making recommendations regarding specific GI siting and design decisions that can maximize provision of ecosystem services.
Section snippets
Description of study sites and monitoring setups
This research was conducted at two bioretention facilities located within two kilometers of one another in Queens, New York City (NYC). The two NYC sites were recently profiled as international examples of nature-based solutions to stormwater in WWAP (United Nations World Water Assessment Programme) (2018). The Colfax and Murdock Avenue bioretention facility (40.702, −73.743) (Site 1 in Fig. 1a) was built in 2010–11. This site receives only direct rainfall and is hydrologically isolated from
Onsite monitored precipitation
Fig. 5a shows the total cumulative depth of seasonal precipitation (e.g. summed over 5 years) at Sites 1 and 2. The seasonal trends were similar between the two sites with cumulative summer totals slightly higher than the other seasons. The 2012 to 2014 precipitation only was used to separate events in order to analyze vertical differences in soil moisture. A total of 151 events were defined from the 5-minute data collected during those periods, with similar distributions observed at the two
Discussion
To discuss these results quantitatively, a logistic regression model was developed to explore the roles of various predictor variables on the observed soil moisture responses. The results, presented in Table 6, indicate that all predictor variables (site, location, season, soil depth, and rainfall depth bin) were significantly correlated to the odds of a soil moisture response. The model demonstrated a reasonable fit, with 84.9% accuracy and AUROC = 0.92.
The odds ratio, exp (β), for the
Conclusions
This study presented observed relationships between the frequency and magnitude of soil moisture responses of engineered GI systems to precipitation, season, soil depth, and HLR, and discussed the potential significance of these responses to the soil–water-climate-vegetation dynamics that underpin GI’s relationship to some ecosystem services and disservices. Variability of soil moisture was more common in the upper soils than in the deeper soils and the magnitude of the response was also
CRediT authorship contribution statement
Bita Alizadehtazi: Conceptualization, Methodology, Software, Visualization, Formal analysis, Data curation, Writing - original draft, Writing - review & editing. Patrick L. Gurian: Formal analysis, Writing - review & editing. Franco A. Montalto: Conceptualization, Supervision, Project administration, Funding acquisition, Writing - review & editing.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
This research was partially funded by the National Science Foundation through CAREER: Integrated Assessments of the Impacts of Decentralized Land Use and Water Management (CBET: 1150994), and Coastal SEES (Track 2), Collaborative: Developing High Performance Green Infrastructure Systems to Sustain Coastal Cities (CMMI: 1325328), and the National Oceanic and Atmospheric Association (NOAA) through Supporting Regional Implementation of Integrated Climate Resilience: Consortium for Climate Risks in
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